Sb uptake and photosynthesis of Zea mays growing in soil watered with Sb mine drainage: an OJIP chlorophyll fluorescence study

Maize (Zea mays) growing in soil watered with Sb mine drainage (SMD) could accumulate Sb and transferred Sb from roots to shoots. The photosynthetic processes in the leaves were clearly inhibited by SMD. Chlorophyll synthesis was inhibited. Photosystem II (PSII) was sensitive to SMD. PSII activity (FV/FM and PIABS) was reduced due to SMD. Irrigation with SMD resulted in an increase in the proportion of the closed PSII reaction centers (RCs) and a decrease in the proportion of QB binding centers. The electron transport on both the donor side and the acceptor side was inhibited by SMD. The total electron transport flux in PSII was reduced and the electron transport beyond QA¯ was the primary target site for toxicity of SMD. PSII RCs were transformed into dissipative sinks for excitation energy under stress of SMD. Sb accumulation in crops due to SMD irrigation may not only reduce crop growth and yield, but also pose a threat to food security and human health.